Processes for the alkylation of aromatic feed stocks and the use of molecular sieves as catalysts in aromatic alkylation process are well known in the art. Such alkylation processes may be used to produce mono- or polyalkylated products ranging from low to high molecular weights and may be carried out in the vapor phase, in the liquid phase, or under intermediate conditions in which both liquid and vapor phases exist.
U.S. Pat. No. 4,185,040 to Ward et al. discloses an alkylation process employing a molecular sieve catalyst of low sodium content which is said to be especially useful in the production of ethylbenzene from benzene and ethylene, and cumene from benzene and propylene. Examples of suitable zeolites include molecular sieves of the X, Y, L, B, ZSM-5, and Omega crystal types, with steam stabilized hydrogen Y zeolite being preferred. The Ward alkylation process may be carried out with either upward or downward flow, the latter being preferred, and preferably under temperature and pressure conditions so that at least some liquid phase is present, at least until substantially all of the olefin alkylating agent is consumed. Ward states that rapid catalyst deactivation occurs under most alkylating conditions when no liquid phase is present.
Another alkylation procedure is disclosed in European Patent Application No. 272,830 to Ratcliffe et al. The Ratcliffe procedure employs molecular sieve alkylation catalysts which have been treated in a manner to improve selectivity to monoalkylation, specifically in the propylation of benzene to produce cumene. Selectivity is said to be increased by at least one percentage point by first depositing a carbonaceous material on the catalyst and then subjecting the resultant carbon containing catalyst particles to combustion. Specifically disclosed zeolitic crystalline molecular sieves include those selected from the group of Y zeolites, fluorided Y zeolites, X zeolites, zeolite beta, zeolite L and zeolite omega. A preferred zeolite is an ammonium exchanged and calcined Y zeolite.
As indicated above, one of the molecular sieve catalysts disclosed in the aforementioned patents to Ward et al. and Ratcliffe et al. is zeolite omega. Crystalline zeolite omega is identified by its characteristic x-ray defraction pattern, and basic procedures for its preparation are disclosed in U.S. Pat. No. 4,241,036 to Flanigan et al. Zeolite omega is described as being capable of absorbing relatively large molecules such as benzene and cyclic compounds, and as being capable of catalyzing various reactions including an alkylation reaction involving propylene and benzene. Flanigan discloses forming a slurry of 10 grams of decationized zeolite omega with 1 gram-mol of benzene and adding excess propylene at room temperature while stirring. A steady rise in temperature was taken as an indication that an exothermic alkylation reaction was occurring and a benzene conversion of 50.9% was obtained after one hour.
A stabilized and dealuminated omega zeolite, as well as a process for its preparation, is disclosed in U.S. Pat. No. 4,724,067, to Raatz et al. The modified omega zeolite is described a exhibiting catalytic activity in the cracking of heavy oil fractions. A preferred process for preparing the stabilized and dealuminated omega zeolite consists of 1) removing the organic cations incorporated during synthesis of the zeolite by roasting in air; 2) exchanging the alkali cations with ammonium cations; 3) calcining in the presence of steam; and 4) acid etching. After modification, the disclosed omega zeolite has a SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio higher than ten (10), and is further characterized by the presence of a particular lattice of secondary pores.
The use of molecular sieves to produce relatively high molecular weight alkyl benzenes which may be used as precursors in the production of alkylarylsulfonate detergents is disclosed in U.S. Pat. No. 4,301,316 to Young. In Young, relatively long chain length alkylating agents having one or more reactive alkyl groups of at least 5 carbon atoms are employed in the alkylation of benzene in the presence of a crystalline zeolite alkylation catalyst. The reactants may be in either the vapor phase or the liquid phase and the zeolite catalysts may be either modified or unmodified. Preferred zeolite catalysts include zeolite beta, ZSM-4, ZSM-20, ZSM-38, and synthetic and naturally occurring isotopes thereof such as zeolite Omega and others. As described in Young, the zeolites may be subject to various chemical treatments including alumina extraction and combination with one or more metal components such as the metals of groups IIB, III, IV, VI, VIIA and VIII. The zeolites may also be subjected to thermal treatments including steaming or calcination in air, hydrogen or an inert gas. Specifically disclosed in Young is the reaction of benzene and 1-dodecene over zeolite HZSM-4 in a flow reactor at 205.degree. C. and 210 psig.
Aromatic alkylation reactions such as the alkylation of benzene with ethylene are highly exothermic reactions and as a result the alkylation reactions may be carried out in stages with intermediate cooling steps. For example, U.S. Pat. No. 4,107,224 to Dwyer, discloses the vapor phase ethylation of benzene over a zeolite catalyst in a down flow reactor with the intermediate injection of cold reactants in a diluent. Specifically disclosed is the interstage injection of ethylene and benzene. Dwyer characterizes the catalysts suitable for use in his invention in terms of those having a constraint index within the approximate range of from 1 to 12. Disclosed as examples of suitable zeolites, with the constraint index in parenthesis, are ZSM-5 (8.3), ZSM-11 (8.7), ZSM-12 (2), ZSM-35 (4.5), ZSM-38 (2) and similar materials. Other molecular sieves, including, ZSM-4 (constraint index 0.5), are disclosed as having constraint indices outside of the range suitable for use in the Dwyer ethylbenzene production process. ZSM-4 is identified in Dwyer (col.10) as "ZSM- 4 (Omega)".